It's been a rocky couple of days for our little planet. Here's what's going on:

A German satellite called ROSAT, launched in 1990 to map X-rays in the sky, is now in a decaying orbit, and Germany's space agency said today it was likely to be caught by the outer layers of the atmosphere sometime Saturday or Sunday.

Like NASA's UARS satellite last month, ROSAT is large enough, and sturdy enough, that pieces of it are likely to survive re-entry. The German Aerospace Center said the odds that somebody, somewhere, could get hit are one in 2,000 -- though your personal chances of being that unlucky someone are more like one in several trillion.

"The main thing we worried about was people getting the wrong message and people panicking," said Mark Matney of NASA's orbital debris office in Houston, which tracked UARS and is now watching ROSAT.

Where and when will the satellite come down? Hard to be precise. Like UARS, it passes 53 degrees north and south of the equator on each orbit, which means it gets as far north as Edmonton, Canada, and as far south as Punta Arenas, Chile.

"It will not be possible to make any kind of reliable forecast about where the satellite will actually come down until about one or two hours before the fact," said Heiner Klinkrad of the European Space Agency. "In the final phase, ROSAT will be 'caught' by the atmosphere at which point ... it will go into 'free fall.'"

After that, some pieces of debris could fall in a narrow oval about 300 miles long. But NASA reminds people that 70 percent of Earth is water, and much of the rest is desert, mountain, tundra or open farmers' fields. Despite the much-debated population explosion, we humans only live on a low percentage of the planet's surface.